An airport electrical power supply is often coupled to an airliner parked on the ground by a workman who pulls the outer end of a power cable to the airplane. Sockets at the end of the cable are mated with pins near the bottom of the aircraft, by the workman pressing the cable end up against the pins, and relying upon friction to hold the cable end in place. The weight of the cable end portion extending down from the aircraft to the ground may be about 15 pounds, and the holding power should be several times as much to assure that an accidental disconnection does not occur. An accidental disconnection can damage the cable end when it hits the ground, and can result in sparks that can ignite fuel. When a disconnection is desired, a technician turns off the power and then pulls, preferably with a force of about 80 pounds, to disconnect the cable end. The withdrawal force must be high, such as about 80 pounds, but must not be much higher than that or disconnection is very difficult.
Considerable current flows to the aircraft, and a low resistance connection is desirable to avoid the creation of high temperatures at the connection. A low resistance connection system which assured a predictable unmating force, would be of considerable value.